GPS微弱信号捕获跟踪算法

在GPS微弱信号捕获算法设计中, 为提高捕获灵敏度, 采用相干积分与非相干积分结合的方式消除数据码长度对相干积分增益的影响, 采用差分相干积分减小非相干积分中的平方衰耗。为了提高信号捕获速度和精度, 利用FFT工具进行伪码与载波频率捕获, 采用延迟锁定环(DLL) 与锁相环(PLL) 实现GPS微弱信号的跟踪。最后对GPS微弱信号的捕获跟踪算法进行仿真实现。应用结果表明: 通过仿真技术能有效地复现出捕获和跟踪载噪比为25dB.Hz^-1的GPS微弱信号, 差分相干积分捕获灵敏度比相干-非相干积分高0.8dB, 频率捕获误差小于1.25Hz, 码捕获误差小于0.1码元。

Acquisition and track algorithm of GPS weak signal

During the design process of acquisition algorithm for GPS weak signal, in order to increase acquisition sensitivity, a method that combined coherent integration with noncoherent integration was adopted to eliminate the influence of data code length on coherent integration gain, and a differential coherent integration was proposed to reduce the square tenuation in noncoherent integration. Instead of traditional methods, FFT-based code and carrier acquisition algorithm was implemented to improve acquisition speed and accuracy. DLL and PLL were used in GPS weak signal track. Finally, the acquisition and track of GPS weak signal were realized by simulation. The result indicates that it is a good approach to track and capture GPS weak signal with the CNR of 25 dB·Hz-1 by simulation technology. The sensitivity of differential coherent acquisition is 0.8 dB larger than the sersitivity of coherent-noncoherent integration, frequency acquisition error is less than 1.25 Hz, and code acquisition error is less than 0.1 code.